Many high temperature applications require a material that is not only processable into a fibrous structure but is also capable of withstanding severe end-use temperatures. In some instances, these temperatures may be as high as 1,000 degrees C to 2,000 degrees C. The existing engineering plastics cannot be used in such applications because most plastics decompose below 1,000 degrees C. Moreover, such plastics suffer dramatic losses in mechanical properties such as tensile strength and tenacity at temperatures as low as 250-400 degrees C. For example, KEVLAR 29 (a trademark of DuPont), when heated to 250 degrees C in air can lose 60% of its tenacity and 60% of its tensile strength. At 425 degrees C Kevlar irreversible degradation and at 500 degrees C KEVLAR decomposes. NOMEX (a trademark of DuPont) decomposes at 370 degrees C and polybenzyimidazole (PBI) decomposes at 480 degrees C. At 520 degrees C, the carbonaceous fibers of the present invention, retain 90% of their original weight.
Heretofore, ceramic graphite fiber and quartz battings and fabrics have been used for high temperature thermal insulation and high temperature protection. All of these prior art materials are very brittle and tend to pack with time and lose loft, thus losing performance with time. The quartz and ceramic materials are air stable at high temperatures such as greater than 450 degrees C. However, they are very difficult for workers to handle and present health risks to the workers similar to those problems created by handling asbestos. A significant amount of research has been conducted by industry to find fibrous materials which can be readily processed into textile batting structures or fabrics and which will withstand temperatures of 400 degrees C or greater in air without loss of mechanical properties. These fibers include Celanese's PBI and Oxidized Polyacrylonitrile Fiber. While these materials are readily processable and have a high degree of resiliency, they lack the requisite thermal stability to withstand temperatures of greater than 400 degrees C and still maintain good mechanical properties.